1. Technical Field
The present invention relates in general to small computer system interface (SCSI) for computers and in particular to a SCSI optical extender that uses fiber optic cable and simple data management to couple and communicate between SCSI interfaces for computer systems and/or devices over extended distances.
2. Description of the Related Art
A small computer system interface (SCSI) is a well known and widely used type of interface in the computer field. A SCSI is generally used to couple a computer system to a device or to couple computer devices together. Communications are provided between a computer system and a device or provided between devices through the SCSI interfaces and by using a SCSI protocol. A SCSI, however, is limited to the distance within which signals may be able to traverse or be transmitted. Typically, signal degradation begins to occur for a SCSI within a twenty (20) meter range.
SCSI extenders were developed to overcome the distance limitations of a SCSI and the degradation of signals through SCSI cables. One conventional SCSI extender converts from SCSI to another protocol, such as fibre channel (FC), to extend the transmission of SCSI signals. Fibre channel (FC) is an optical form of transmission. A SCSI to FC converter is used to convert SCSI signals to FC signals. A fibre channel protocol is used to process the transmission of the fibre channel signals. A FC to SCSI converter is then used to convert the FC signals back into SCSI signals. However, latency exists for such SCSI extenders since data has to be buffered and conversion to another protocol needs to be implemented for extending SCSI communications. Therefore, drawbacks to SCSI extenders that use protocol conversion, such as the SCSI to FC and FC to SCSI conversion process, are that such implementations require buffering of data, conversion processes and algorithms, conversion hardware, error recovery code, extensive micro-code or programming, and other such additional hardware and software for implementing protocol conversion in extending SCSI communications, which all add to the cost of the overall system and method and make the overall system and method more complex. Thus, such SCSI extenders that implement conversion processes and systems are relatively expensive.
It would therefore be advantageous and desirable to provide an improved system and method for extending interface communications for a SCSI. It would also be advantageous and desirable to have a system and method of providing SCSI extenders that are able to extend SCSI communications over relatively long distances while also being fast and efficient in operation and inexpensive in implementation. It would also be advantageous and desirable to provide a system and method to extend SCSI communications which reduces latency, buffering, error recovery code, and other such additional hardware and software. It would be advantageous and desirable to provide a system and method which avoids having to convert from SCSI to another protocol and then from the other protocol back to SCSI, such as from SCSI to FC and back from FC to SCSI, in order to provide extended communications for SCSI.
It is therefore one object of the present invention to provide an improved system and method for extending communications and interfaces for a SCSI.
It is another object of the present invention to provide a system and method of providing SCSI extenders that are able to extend SCSI communications over relatively long distances while also being fast and efficient in operation and inexpensive in implementation.
It is still another object of the present invention to provide a system and method to extend SCSI communications which reduces latency, buffering, error recovery code, and other such additional hardware and software.
It is a further object of the present invention to provide a system and method which avoids having to convert from SCSI to another protocol and then from the other protocol back to SCSI, such as from SCSI to FC and back from FC to SCSI, in order to provide extended communications for SCSI.
The foregoing objects are achieved as is now described. An improved system and method for extending interface communications for a SCSI. The system and method provides SCSI extenders that are able to extend SCSI communications over relatively long distances between at least two SCSI interfaces while also being fast and efficient in operation and inexpensive in implementation. The present system and method reduces latency, buffering, error recovery code, and other such additional hardware and software. SCSI signals are received from one SCSI interface, and the SCSI signals from the one SCSI interface are parallel loaded into a parallel register. The SCSI signals from the one SCSI interface are serialized into serial data, and the serial data from the parallel register is transmitted over an optical communication system. The transmitted serial data is converted back to the SCSI signals that were originally from the one SCSI interface. The SCSI signals that were originally from the one SCSI interface are received by and shifted into a data management and driver system, and the data management and driver system is used to manage and drive the SCSI signals from the one SCSI interface to another SCSI interface. The same system and methodology is applied to extend communications in both directions between the at least two SCSI interfaces. The data management and driver system arbitrates, selects, and drives SCSI signals from one SCSI interface to another SCSI interface. The data management and driver system includes a receive serial shift register and a driver logic device.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.